Friday, April 29, 2016

May is a Good Time for Invasive Shrub Control in Prairies and Savannas

At Black Earth Rettenmund Prairie we have three burn units,
and burn each on a rotation of two out of each three years. Thus, each year we
have one unburned unit and two burned ones. Each year a different unit is left
unburned.

The unburned unit is the one in which we do invasive shrub
control.

Invasive shrub control focuses on the unit which is in its “off”
burn year. Invasive brush in that unit is easy to find, because the
above-ground buds are alive and leaf out. They are thus easy to find during a stroll
through the unit and are easy to kill because they are not very large.

How to kill the invasive shrubs?

If it is a single isolated
plant: cut each stem of that plant with a hand clippers and treat the cut
stem with herbicide (Garlon 4 at 20% concentration in bark oil)

Or: don’t cut but treat
the stem near the base (basal bark) with Garlon

If it is a large clone
such as one often finds with aspen, hazel, buckthorn, or sumac: cut the
whole clone with a power brushcutter and treat each cut stem with Garlon

For isolated stems of
a straight-growing plant like aspen: swipe up from the base of each stem with a sponge stick
loaded with Garlon in oil

This “one-out-of-three” approach makes a lot of sense,
because you only have to do invasive shrubs in one-third of the prairie.

Hopefully, there are no invasive shrubs in the two units
that were burned this spring. However, any straggling invasive shrubs that
might be present would have been top-killed so they do not leaf out.

However, if there are still invasive shrubs in the units
that have been burned, they can be dealt with later in the summer when they
have resprouted and are tall enough to find. Or even better, wait until late
fall, after all the native vegetation has senesced, and the invasive shrubs can
be found more easily. Then use one of the treatment methods listed above.

Note that invasive brush can also be worked on all winter,
even when there are no leaves. Again, any of the methods listed above can be
used.

An important point: you can’t eradicate invasive brush in a
single year. It is essential to return year after year, since there will be
resprouts or root suckers or new seedlings which will turn into shrubs. Keep at
it.

Black Earth Rettenmund Prairie looking south across the
Saddle Unit from the North Unit. The brown patch in the background is the
unburned South Unit, where brush control will be carried out.

Wednesday, April 20, 2016

Smooth Patch: An interesting bark condition on bur oaks

Mature bur oak trees have very thick bark with deep ridges.
You can almost bury a pencil within the tree’s crevices. However, occasional
trees have areas on the trunk that have sloughed off that outer thick bark,
exposing a lighter inner smooth bark. Such a condition is called “smooth patch”
and it is caused by infection with the fungus Aleurodiscus oaksii.According to University of Minnesota Forestry,
the fungus does not attack living plant parts and no control is necessary.

An area on "smooth patch" on a large bur oak in Unit 10 savanna.Most bur oak trees at PVC do not exhibit this condition.

Friday, April 15, 2016

There was a time when dead wood lying on the forest floor
was looked at as undesirable. This probably derived from those historic times
when wood was the major source of heat for rural homes and wood of any size or
shape was used as kindling or fire wood.

Those days are long past. What is now called coarse woody
debris (CWD) is known to play major roles in ecosystem function. At one time
“dead wood” was the bane of foresters but now it is considered an environmental
boon. The US Forest Service, since the 1970s, has recognized the importance of
CWD in forests and has published the research described in several conferences.

The British were probably the first to recognize the
importance of CWD. Here is an early (1966) quote from Animal Population
Ecologist Charles Elton concerning the state of British woods: “When one walks
through the rather dull and tidy woodlands…that result from modern forestry
practices, it is difficult to believe that dying and dead wood provides one of
the two or three greatest resources for animal species in a natural forest, and
that if fallen timber and slightly decayed trees are removed the whole system
is gravely impoverished of perhaps more than a fifth of its fauna.”

According to Elton, and confirmed from numerous later
studies, large numbers of species of animals live in wood or under bark. Fungi,
especially lignin digesters such as basidiomycetes, use wood as their principal
carbon and energy source. Birds, small mammals, and other critters thrive on
CWD. Research has shown that biodiversity is many-fold higher with CWD on the
ground than without it.

Why encourage CWD?

Important component of a forest
ecosystem

Major habitat of arthropods (many
species)

Mites

Bark beetles

Wood borers

Carpenter ants

wasps

Provide nesting, roosting,
feeding, and shelter sites for birds

Haven for

Small mammals

Reptiles

Amphibians

Reduce erosion

Important for soil development

Store nutrients and water

Provide source of energy and
nutrient flow in the system

Serve as seedbeds for forbs and
grasses

Mosses (bryophytes) especially
grow on CWD

Provide habitat for decomposers,
especially fungi

Fungi are a very diverse greoup of
organisms that are essential for other organisms that depend on CWD and
ecosystem functioning

CWD is an important indicator of a
“natural” forest

Carbon sequestration (significant
for climate change studies)

Nature’s unsung heroes of
recycling

Examples of important species in recycling

Fungi (most important
biochemically)

Beetles

Flies and maggots

Wood lice

Slime molds

Bacteria

Slugs

Snails

Millipedes

Springtails

Earthworms

Animals and fungi work together in the decomposition of CWD.
Smaller particles decompose more rapidly than larger, so that insects and other
animals that physically break down large pieces of wood, greatly increase
fungal activity. On the other hand, fungal infection promotes insect attack,
creating a feedback loop that greatly increases the rate of CWD decay.

Note that the animals involved in CWD decomposition are
different species from those that affect (grow on) living trees.

Coarse woody debris is much more common in unmanaged than in
managed forests. CWD is an indicator of an “old-growth”forest, as well as an
indicator of a high-biodiversity environment.

Stumps are a separate category. A stump has an above-ground
and a below-ground component. The below-ground portion is very important. As
much as 80% of total CWD carbon of a stump can be below ground (hidden).

From the time it dies, a dead tree contributes to many
ecological processes

As a standing snag

As a major piece of fallen woody material lying on and in
the soil

Fuel for fire

Biological decomposition

Which is the most important in recycling of CWD, fire or
biological activity? It depends on the species of wood, and the environment, Without fire nutrients may be tied up in dead woody material
for a long time.

Rate of decomposition varies greatly among the tree species.
Oaks of the white-oak group (white, bur, swamp white) are the most resistant to
decay.

Especially in colder climates, dead wood lasts a long time
on the ground, slowly being converted into carbon dioxide, minerals, humus, and
living critters. The rate of decay will depend upon the species, the size,
shape, and position relative to the forest floor, fire, and other factors.

Carbon release from decaying wood is a major component of
the global carbon balance and hence of major importance in climate-change
studies.

Wood decomposition is an aerobic process although slow
because of the presence of lignin in the heartwood. Lignin decomposition takes place primarily by white-rot fungi (Basidiomycetes).
Lignin is one of the mostly slowly decomposing components of wood. Because of
this, significant amounts of lignin remain when the other principal biochemical
components of wood, cellulose and hemicellulose, have been degraded. Residual
lignin is a major fraction of the soil humus.

Snags were once considered safety hazards and down wood was
considered unsightly, a haven for pests, and a fire hazard. Snags may still be
a safety hazard but the probability of falling at an inappropriate time is very
low. Snags are major habitats for birds.

Coarse woody debris
at Pleasant Valley Conservancy.

We don’t need quantitative methods to discern that the CWD
varies markedly from habitat to habitat at PVC.

Prairies, of course, have almost no CWD, whereas dense
woods, such as the north-facing slope, have large amounts. See last December's post. Closed savannas have
more CWD than open savannas. In wetlands the amount of CWD varies. Stream
banks, with lots of willows, have lots of CWD, both near the bank and submerged
in the water.

Oak savanna (Unit 19E) with scattered CWD.Note also the dead oaks in the background,destined to become future CWD

This dead oak came down after the fire of 3-29-2016. Note that none of the wood is charred except the base..The dead base was weakened by the fire, and the snag came down in the next windstorm.

The top end of the burned snag shown in the above photo. Lots of potential CWD here!

The cracks and tarnish indicate that this log has been down for some years.Note all the plants that are growing in and among this CWD.